SCons 4.9.0 is available

Expose the extra_libs keyword argument in CheckLibWithHeader and 'CheckLib'

Removed Python 3.6 support.

Override environments, created when giving construction environment keyword arguments to Builder calls (or manually, through the undocumented Override method), were modified not to "leak" on item deletion. The item will now not be deleted from the base environment.

Added support for tracking beamer themes in the LaTeX scanner.

MSVS: msvs project files are always generated before the corresponding msvs solution files. This changes the behavior of clean for a project generated with auto_build_solution disabled and explicit solution generation: when the solution files are cleaned, the project files are also cleaned. The tests for vs 6.0-7.1 were updated accordingly.

MSVS: Add an optional keyword argument, auto_filter_projects, to MSVSSolution. Accepted values for auto_filter_projects are:

• None [default]: raise an exception when solution file names or nodes are detected in the projects argument list.
• True or evaluates True: automatically remove solution file names and nodes from the project argument list.
• False or evaluates False: leave solution file names and nodes in the project argument list. An exception is not raised.

Solution file names and/or nodes in the project argument list cause erroneous Project records to be produced in the generated solution file. As a convenience, a user may elect to ignore solution file names and nodes in the projects argument list rather than manually removing solution file names and nodes from the MSVSProject return values.

SCons C preprocessor:

• Update the optional integer suffixes to include the z|Z and wb|WB suffixes.
• Add support for binary integer constants.
• Add support for octal integer constants. Previously, octal integers were evaluated as decimal integers. A literal zero (0) is treated as an octal number.
• Change the method for attempted conversion of a define expansion value to an integer from a literal to a constant expression evaluation.

Add a tag to each CacheDir to let systems ignore backing it up (per https://bford.info/cachedir/). Update the way a CacheDir is created, since it now has to create two files.

The Dictionary method now has an as_dict flag. If true, Dictionary always returns a dict. The default remains to return different types depending on whether zero, one, or multiple construction

A Variables object now makes available a "defaulted" attribute, a list of variable names that were set in the environment with their values taken from the default in the variable description (if a variable was set to the same value as the default in one of the input sources, it is not included in this list).

If a build Variable is created with no aliases, the name of the Variable is no longer listed in its aliases. Internally, the name and aliases are considered together anyway so this should not have any effect except for being visible to custom help text formatters.